﻿using System;
using System.Collections.Generic;
using Crayon.ParseTree;

namespace Crayon.Translator.Python
{
	internal class PythonTranslator : AbstractTranslator
	{
		public PythonTranslator()
			: base()
		{ }

		public void TranslateListDefinition(List<string> output, ListDefinition list)
		{
			output.Add("[");
			for (int i = 0; i < list.Items.Length; ++i)
			{
				if (i > 0)
				{
					output.Add(", ");
				}

				this.TranslateExpression(output, list.Items[i]);
			}
			output.Add("]");
		}

		protected override void TranslateDotStepStruct(List<string> output, DotStepStruct dotStepStruct)
		{
			output.Add(dotStepStruct.RootVar);
			output.Add("[");
			output.Add(dotStepStruct.StructDefinition.IndexByField[dotStepStruct.FieldName].ToString());
			output.Add("]");
		}

		protected override void TranslateSwitchStatementContinuousSafe(List<string> output, SwitchStatementContinuousSafe switchStatement)
		{
			SwitchStatementContinuousSafe.SearchTree tree = switchStatement.GenerateSearchTree();
			int switchId = this.GetNextInt();
			string varName = "switch_key_" + switchId;
			output.Add(this.CurrentTabIndention);
			output.Add(varName);
			output.Add(" = ");
			this.TranslateExpression(output, switchStatement.Condition);
			output.Add("\r\n");
			this.GenerateSearchTree(output, tree, varName);
		}

		private void GenerateSearchTree(List<string> output, SwitchStatementContinuousSafe.SearchTree tree, string varName)
		{
			if (tree.Code == null)
			{
				output.Add(this.CurrentTabIndention);
				output.Add("if " + varName + " < " + tree.LessThanThis + ":\r\n");
				this.CurrentIndention++;
				this.GenerateSearchTree(output, tree.Left, varName);
				this.CurrentIndention--;
				output.Add(this.CurrentTabIndention);
				output.Add("else:\r\n");
				this.CurrentIndention++;
				this.GenerateSearchTree(output, tree.Right, varName);
				this.CurrentIndention--;
			}
			else
			{
				this.Translate(output, tree.Code);
			}
		}

		protected override void TranslateSwitchStatementUnsafeBlotchy(List<string> output, SwitchStatementUnsafeBlotchy switchStatement)
		{
			string lookupName = switchStatement.LookupTableName;
			string varName = "switch_key_" + this.GetNextInt();

			if (switchStatement.UsesStrings)
			{
				output.Add(this.CurrentTabIndention);
				output.Add(varName);
				output.Add(" = ");
				output.Add("v_" + lookupName);
				output.Add(".get(");
				this.TranslateExpression(output, switchStatement.Condition);
				output.Add(", " + switchStatement.DefaultCaseId);
				output.Add(")\r\n");
			}
			else
			{
				output.Add(this.CurrentTabIndention);
				output.Add(varName);
				output.Add(" = ");
				output.Add("v_" + lookupName);
				output.Add("[");
				this.TranslateExpression(output, switchStatement.Condition);
				output.Add("]\r\n");
			}

			this.GenerateSearchTree(output, switchStatement.GenerateSearchTree(), varName);
		}

		protected override void TranslateFloatConstant(List<string> output, FloatConstant floatConstant)
		{
			output.Add(Util.FloatToString(floatConstant.Value));
		}

		protected override void TranslateBooleanNot(List<string> output, BooleanNot booleanNot)
		{
			output.Add("not (");
			this.TranslateExpression(output, booleanNot.Root);
			output.Add(")");
		}

		protected override void TranslateBooleanCombination(List<string> output, BooleanCombination booleanCombination)
		{
			output.Add("(");
			this.TranslateExpression(output, booleanCombination.Expressions[0]);
			output.Add(")");

			for (int i = 0; i < booleanCombination.Ops.Length; ++i)
			{
				if (booleanCombination.Ops[i].Value == "&&")
				{
					output.Add(" and ");
				}
				else
				{
					output.Add(" or ");
				}

				output.Add("(");
				this.TranslateExpression(output, booleanCombination.Expressions[i + 1]);
				output.Add(")");
			}
		}

		protected override void TranslateNegativeSign(List<string> output, NegativeSign negativeSign)
		{
			output.Add("-(");
			this.TranslateExpression(output, negativeSign.Root);
			output.Add(")");
		}

		protected override void TranslateStringConstant(List<string> output, StringConstant stringConstant)
		{
			output.Add("\"");
			string value = stringConstant.Value;
			foreach (char c in value)
			{
				string nc = "" + c;
				switch (c)
				{
					case '\\': nc = "\\\\"; break;
					case '"': nc = "\\\""; break;
					case '\0': nc = "\\0"; break;
					case '\t': nc = "\\t"; break;
					case '\n': nc = "\\n"; break;
					case '\r': nc = "\\r"; break;
					default: break;
				}
				output.Add(nc);
			}
			output.Add("\"");
		}

		protected override void TranslateReturnStatement(List<string> output, ReturnStatement returnStatement)
		{
			output.Add(this.CurrentTabIndention);
			output.Add("return");
			if (returnStatement.Expression != null)
			{
				output.Add(" ");
				TranslateExpression(output, returnStatement.Expression);
			}
			output.Add("\r\n");
		}

		protected override void TranslateBreakStatement(List<string> output, BreakStatement breakStatement)
		{
			output.Add(this.CurrentTabIndention);
			output.Add("break\r\n");
		}

		protected override void TranslateDotStep(List<string> output, DotStep dotStep)
		{
			output.Add("(");
			TranslateExpression(output, dotStep.Root);
			output.Add(")");
			output.Add(".f_");
			output.Add(dotStep.StepToken.Value);
		}

		protected override void TranslateSwitchStatement(List<string> output, SwitchStatement switchStatement)
		{
			int switchId = this.GetNextInt();

			if (switchStatement.UsesStrings)
			{
				throw new NotImplementedException("Create a string dictionary lookup");
			}
			else if (switchStatement.IsSafe && switchStatement.IsContinuous)
			{
				this.TranslateSwitchStatementAsBinaryDecisions(output, switchStatement, switchId, false);
			}
			else
			{
				this.TranslateSwitchStatementAsElifChain(output, switchStatement, switchId);
			}
		}

		private void TranslateSwitchStatementAsBinaryDecisions(List<string> output, SwitchStatement switchStatement, int switchId, bool doSafeMapping)
		{

		}

		private void TranslateSwitchStatementAsElifChain(List<string> output, SwitchStatement switchStatement, int switchId)
		{
			output.Add(this.CurrentTabIndention);
			output.Add("switch_loopy_" + switchId + " = 1\r\n");
			output.Add(this.CurrentTabIndention);
			output.Add("while switch_loopy_" + switchId + " == 1:\r\n");
			this.CurrentIndention++;
			output.Add(this.CurrentTabIndention);
			output.Add("switch_loopy_" + switchId + " = 0\r\n");

			Expression firstCase = switchStatement.Chunks[0].Cases[0];
			if (firstCase == null)
			{
				// WAT
				throw new Exception("This should have been optimized out.");
			}
			else if (firstCase is IntegerConstant)
			{
				// TODO: do this for real
				// There are several optimziations that can be done.
				// if it's a small switch, just use if/elif/else
				// if it's all positive and condensed and ordered, use a binary search with if/else
				// if they're sparse, are they super sparse?
				// if they're chunked not in order, normalize them with a static int-to-int array
				// if there are any weird breaks that aren't at the end, you need to put the whole thing in a one-time loop. e.g. "for ignored in (1,):"
				// now I feel sad. Here's a big-ass if/elif/else chain.
				string varName = "switch_expr_" + switchId;

				output.Add(this.CurrentTabIndention);
				output.Add(varName);
				output.Add(" = ");
				TranslateExpression(output, switchStatement.Condition);
				output.Add("\r\n");

				/*
				 * This is probably best
				 * _switch_statement_lookup_27 = {
				 *   case_expr1: 1,
				 *   case_expr2a: 2,
				 *   case_expr2b: 2,
				 *   case_expr3: 3
				 * }
				 * ...
				 * _ignored_switch_loopy_thing_27 = 1
				 * while _ignored_switch_loopy_thing_27 == =1:
				 *   _ignored_switch_loopy_thing = 0
				 *   _switch_expr_27 = _switch_statement_lookup_27.get(arbitrary_expression, 4) # 4 is the default case
				 *   if _switch_expr_27 < 3:
				 *     if _switch_expr_27 < 2:
				 *       code for case 1
				 *     else:
				 *       code for case 2
				 *   else:
				 *     if _switch_expr_27 < 4:
				 *       code for case 3
				 *     else:
				 *       code for case 4 (default)
				 * 
				 * This way you just leave the breaks as they are. 
				 * Don't try to use an array instead of a dictionary, though. Because that will cause the switch to crash if a crazy value is passed in.
				 */


				// This isn't even right. If a default is first, this will blow up.
				for (int i = 0; i < switchStatement.Chunks.Length; ++i)
				{
					SwitchStatement.Chunk chunk = switchStatement.Chunks[i];
					bool conditionRequired = true;
					output.Add(this.CurrentTabIndention);
					if (i == 0)
					{
						output.Add("if ");
					}
					else if (chunk.Cases[chunk.Cases.Length - 1] == null)
					{
						output.Add("else:\r\n");
						conditionRequired = false;
					}
					else
					{
						output.Add("elif ");
					}

					if (conditionRequired)
					{
						bool parens = chunk.Cases.Length > 1;

						if (parens)
						{
							output.Add("(");
						}

						for (int j = 0; j < chunk.Cases.Length; ++j)
						{
							if (j > 0)
							{
								output.Add(") or (");
							}

							output.Add(varName);
							output.Add(" == ");
							TranslateExpression(output, chunk.Cases[j]);
						}

						if (parens)
						{
							output.Add(")");
						}

						output.Add(":\r\n");
						this.CurrentIndention++;

						Translate(output, chunk.Code);

						if (chunk.Code.Length == 0)
						{
							output.Add(this.CurrentTabIndention);
							output.Add("pass\r\n");
						}

						this.CurrentIndention--;
					}
					else
					{
						this.CurrentIndention++;

						Translate(output, chunk.Code);

						if (chunk.Code.Length == 0)
						{
							output.Add(this.CurrentTabIndention);
							output.Add("pass\r\n");
						}

						this.CurrentIndention--;
					}
				}


			}
			else if (firstCase is StringConstant)
			{
				throw new NotImplementedException("switch on string not implemented yet.");
			}
			else
			{
				throw new ParserException(firstCase.FirstToken, "Invalid value for a switch statement case.");
			}

			this.CurrentIndention--;
		}

		protected override void TranslateBooleanConstant(List<string> output, BooleanConstant booleanConstant)
		{
			output.Add(booleanConstant.Value ? "True" : "False");
		}

		protected override void TranslateWhileLoop(List<string> output, WhileLoop whileLoop)
		{
			output.Add(this.CurrentTabIndention);
			output.Add("while ");
			this.TranslateExpression(output, whileLoop.Condition);
			output.Add(":\r\n");
			this.CurrentIndention++;
			this.Translate(output, whileLoop.Code);
			this.CurrentIndention--;
		}

		protected override void TranslateExpressionAsExecutable(List<string> output, ExpressionAsExecutable exprAsExec)
		{
			output.Add(this.CurrentTabIndention);
			TranslateExpression(output, exprAsExec.Expression);
			output.Add("\r\n");
		}

		protected override void TranslateBracketIndex(List<string> output, BracketIndex bracketIndex)
		{
			TranslateExpression(output, bracketIndex.Root);
			output.Add("[");
			TranslateExpression(output, bracketIndex.Index);
			output.Add("]");
		}

		protected override void TranslateFunctionCall(List<string> output, FunctionCall functionCall)
		{
			TranslateExpression(output, functionCall.Root);
			output.Add("(");
			for (int i = 0; i < functionCall.Args.Length; ++i)
			{
				if (i > 0) output.Add(", ");
				TranslateExpression(output, functionCall.Args[i]);
			}
			output.Add(")");
		}

		protected override void TranslateNullConstant(List<string> output, NullConstant nullConstant)
		{
			output.Add("None");
		}

		protected override void TranslateIntegerConstant(List<string> output, IntegerConstant intConstant)
		{
			int value = intConstant.Value;
			if (value >= 0)
			{
				output.Add("" + value);
			}
			else
			{
				output.Add("(" + value + ")");
			}
		}

		protected override void TranslateStructInstance(List<string> output, StructInstance structInstance)
		{
			output.Add("[");
			for (int i = 0; i < structInstance.Args.Length; ++i)
			{
				if (i > 0) output.Add(", ");
				this.TranslateExpression(output, structInstance.Args[i]);
			}
			output.Add("]");
		}

		protected override void TranslateAssignment(List<string> output, Assignment assignment)
		{
			output.Add(this.CurrentTabIndention);
			this.TranslateExpression(output, assignment.Target);
			output.Add(" ");
			output.Add(assignment.AssignmentOp);
			output.Add(" ");
			this.TranslateExpression(output, assignment.Value);
			output.Add("\r\n");
		}

		protected override void TranslateIfStatement(List<string> output, ParseTree.IfStatement exec)
		{
			output.Add(this.CurrentTabIndention);
			output.Add("if ");
			TranslateExpression(output, exec.Condition);
			output.Add(":\r\n");
			this.CurrentIndention++;
			if (exec.TrueCode.Length == 0)
			{
				output.Add(this.CurrentTabIndention);
				output.Add("pass\r\n");
			}
			else
			{
				Translate(output, exec.TrueCode);
			}
			this.CurrentIndention--;
			if (exec.FalseCode.Length > 0)
			{
				output.Add(this.CurrentTabIndention);
				output.Add("else:\r\n");
				this.CurrentIndention++;
				Translate(output, exec.FalseCode);
				this.CurrentIndention--;
			}
		}

		protected override void TranslateForLoop(List<string> output, ParseTree.ForLoop exec)
		{
			Translate(output, exec.Init);
			output.Add(this.CurrentTabIndention);
			output.Add("while ");
			TranslateExpression(output, exec.Condition);
			output.Add(":\r\n");
			this.CurrentIndention++;
			Translate(output, exec.Code);
			Translate(output, exec.Step);
			this.CurrentIndention--;
		}

		protected override void TranslateVariable(List<string> output, ParseTree.Variable expr)
		{
			output.Add(this.GetVariableName(expr.Name));
		}

		protected override string TabString { get { return "\t"; } }

		protected override void TranslateFunctionDefinition(List<string> output, ParseTree.FunctionDefinition functionDef)
		{
			output.Add(this.CurrentTabIndention);
			output.Add("def v_");
			output.Add(functionDef.NameToken.Value);
			output.Add("(");
			for (int i = 0; i < functionDef.ArgNames.Length; ++i)
			{
				if (i > 0) output.Add(", ");
				output.Add("v_" + functionDef.ArgNames[i].Value);
			}
			output.Add("):\r\n");
			this.CurrentIndention++;
			Translate(output, functionDef.Code);
			this.CurrentIndention--;
			output.Add("\r\n");
		}
	}
}
